Communication system and method for an optical local area network

ABSTRACT

An optical local area network includes a passive optical distribution fabric interconnecting a plurality of nodes including a first node and a plurality of remaining nodes, a hub that includes the first node and a control module, and a client network adapter coupled to each of the remaining nodes for responding to the control module. The control module controls timing for each of the client network adapters to transmit signals over the passive optical distribution fabric and distribution of signals to each of the nodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is filed under 37 C.F.R. § 1.53(b) as a continuationclaiming the benefit under 35 U.S.C. § 120 of the pending patentapplication Ser. No. 17/138,794, “Communication System and Method for anOptical Local Area Network”, which was filed by the same inventors onDec. 30, 2020, claiming the benefit under 35 U.S.C. § 120 of the pendingpatent application Ser. No. 16/866,479, “Communication System and Methodfor an Optical Local Area Network”, which was filed by the sameinventors on May 4, 2020, claiming the benefit under 35 U.S.C. § 120 ofthe pending patent application Ser. No. 16/734,270, “CommunicationSystem and Method for an Optical Local Area Network”, which was filed bythe same inventors on Jan. 3, 2020, claiming the benefit under 35 U.S.C.§ 120 of the pending patent application Ser. No. 14/588,899, “System andMethod for Optical Layer Management in Optical Modules and RemoteControl of Optical Modules”, which was filed by the same inventors onJan. 2, 2015, claiming the benefit under 35 U.S.C. § 120 of the pendingpatent application Ser. No. 13/543,880, “System and Method for OpticalLayer Management in Optical Modules and Remote Control of OpticalModules”, which was filed by the same inventors on Jul. 8, 2012,claiming the benefit under 35 U.S.C. § 120 of the pending patentapplication Ser. No. 12/982,872, “System and Method for PluggableOptical Modules for Passive Optical Networks”, which was filed by thesame inventors on Dec. 30, 2010, claiming the benefit under 35 U.S.C. §120 of U.S. Pat. No. 7,925,162 filed on Jul. 6, 2004 claiming thebenefit under 35 U.S.C. 119(e) of U.S. Provisional Application No.60/485,072 filed Jul. 3, 2003, now expired, and U.S. ProvisionalApplication No. 60/515,836 filed Oct. 30, 2003, now expired; andclaiming the benefit under 35 U.S.C. § 120 of the pending patentapplication Ser. No. 12/512,968, “System and Method For Performing HighSpeed Communications Over Fiber Optical Networks”, which was filed bythe same inventors on filed Jul. 30, 2009 claiming the benefit under 35U.S.C. § 120 of U.S. patent application Ser. No. 11/772,187, which wasfiled by the same inventors on Jun. 30, 2007, now abandoned, claimingthe benefit under 35 U.S.C. § 120 of commonly-assigned U.S. patentapplication Ser. No. 10/865,547 filed by the same inventors on Jun. 10,2004, now U.S. Pat. No. 7,242,868, which claims the benefit under 35U.S.C. 119(e) of U.S. Provisional Application No. 60/477,845 filed Jun.10, 2003, now expired, and U.S. Provisional Application No. 60/480,488filed Jun. 21, 2003, now expired, and entirely incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to optical fiber networks.

BACKGROUND OF THE INVENTION

A local-area network (LAN) is a computer network that spans a relativelysmall area or domain. Most LANs are confined to a single building orgroup of buildings. However, one LAN can be connected to other LANs overany distance often spanning an area greater than either LAN viatelephone lines, coaxial cable, optical fiber, free-space optics andradio waves. A system of LANs can be connected in this way via othernetworks that are commonly referred to as wide-area networks (WANs).

SUMMARY OF THE INVENTION

In general, in one aspect, the invention includes a method forbroadcasting data including receiving an incoming optical signal at afirst port of a plurality of ports; converting the received incomingoptical signal to an electrical signal; processing the electricalsignal; converting the processed electrical signal to a broadcastoptical signal; and coupling the broadcast optical signal to each of theplurality of ports.

Aspects of the invention may include one or more of the followingfeatures. Processing the electrical signal includes coupling theelectrical signal to a device that processes the electrical signalaccording to an OSI layer-2 protocol. Processing the electrical signalincludes coupling the electrical signal to a device that processes theelectrical signal according to an OSI layer-3 protocol. The methodfurther includes converting an electrical client signal to the incomingoptical signal. The method further includes adapting the electricalclient signal from a signal conforming to an OSI layer-2 protocol. TheOSI layer-2 protocol includes a media access control protocol. The mediaaccess control protocol is Ethernet or Fibre Channel. The method furtherincludes transmitting the incoming optical signal from a network clientadapter to one of the plurality of ports over an optical distributionfabric. The method further includes transmitting the broadcast opticalsignal from one of the plurality of ports over an optical distributionfabric; and receiving the broadcast optical signal at network clientadapters in a plurality of clients. The method further includesconverting the received broadcast optical signal to a second electricalsignal in at least one of the clients. The method further includesselecting a frame within the second electrical signal associated withthe network client adapter and adapting data in the selected frame fortransmission over a network interface.

In general, in another aspect, the invention includes an apparatusincluding a plurality of ports; a passive optical coupler coupled toeach of the plurality of ports; an optical-electrical converter inoptical communication with the passive optical coupler; and a controlmodule in electrical communication with the optical-electrical converterfor scheduling slots for incoming and outgoing signals over theplurality of ports.

Aspects of the invention may include one or more of the followingfeatures. The control module is operable to schedule a slot forreceiving a signal over one of the plurality of ports and to schedule aslot for broadcasting a signal over each of the plurality of ports. Theapparatus includes only a single optical-electrical converter in opticalcommunication with the passive optical coupler. The control module iscoupled to a device that is operable to process an electrical signalprovided by the optical-electrical converter according to an OSI layer-2protocol. The control module is coupled to a device that is operable toprocess an electrical signal provided by the optical-electricalconverter according to an OSI layer-3 protocol.

In general, in another aspect, the invention includes an optical localarea network including a plurality of optical waveguides; a networkmanager that includes an optical-electrical converter in opticalcommunication with the plurality of optical waveguides; and a controlmodule in electrical communication with the optical-electrical converterfor scheduling slots for incoming and outgoing signals transmitted overthe plurality of optical waveguides; and a plurality of network clientadapters coupled to the plurality of optical waveguides, each networkclient adapter including an optical-electrical converter for processingtransmitted and received optical signals at a client.

Aspects of the invention may include one or more of the followingfeatures. The optical local area network further includes a passiveoptical coupler coupled to each of the plurality of optical waveguides.The network manager further includes a passive optical coupler coupledto each of the plurality of optical waveguides. The control module isoperable to schedule a slot for receiving a signal over one of theplurality of optical waveguides and to schedule a slot for broadcastinga signal over each of the plurality of optical waveguides. The controlmodule is operable to dynamically schedule a slot for receiving a signalover one of the plurality of optical waveguides in response to a messagefrom one of the network client adapters. The control module is operableto determine a response delay between the optical-electrical converterand one of the network client adapters. The control module is coupled toa device that is operable to process an electrical signal provided bythe optical-electrical converter according to an OSI layer-2 protocol.The control module is coupled to a device that is operable to process anelectrical signal provided by the optical-electrical converter accordingto an OSI layer-3 protocol. Each of the network client adapters isoperable to convert an electrical client signal to an optical signal fortransmission over one of the optical waveguides. Each of the networkclient adapters is operable to adapt the client signal from a signalconforming to an OSI layer-2 protocol. The OSI layer-2 protocol includesa media access control protocol. The media access control protocol usedby a network client adapter is Ethernet or Fibre Channel. Each of thenetwork client adapters is operable to convert a received optical signalto an electrical signal. Each network client adapter is operable toselect a frame within the electrical signal associated with the networkclient adapter. The optical local area network further includes a clientthat includes a network interface card, the network interface cardincluding one of the network client adapters. The client is selectedfrom the group consisting of a workstation, a personal computer, a diskstorage array, a server, a switch, and a router.

In general, in another aspect, the invention includes an optical localarea network including a passive optical distribution fabricinterconnecting a plurality of nodes including a first node and aplurality of remaining nodes; a hub that includes the first node and acontrol module; and a client network adapter coupled to each of theremaining nodes for responding to the control module; wherein thecontrol module controls timing for each of the client network adaptersto transmit signals over the passive optical distribution fabric anddistribution of signals to each of the nodes.

Aspects of the invention may include one or more of the followingfeatures. The control module is operable to schedule a slot forreceiving a signal from one of the remaining nodes and to schedule aslot for broadcasting a signal to each of the remaining nodes. Thecontrol module is operable to dynamically schedule a slot for receivinga signal from one of the remaining nodes in response to a message fromone of the network client adapters. The control module is operable todetermine a response delay between the hub and one of the network clientadapters. The control module is coupled to a device that is operable toprocess signals according to an OSI layer-2 protocol. The control moduleis coupled to a device that is operable to process signals according toan OSI layer-3 protocol. Each of the network client adapters is operableto convert an electrical signal to an optical signal for transmissionover the passive optical transmission fabric. Each of the network clientadapters is operable to adapt a signal conforming to an OSI layer-2protocol. The OSI layer-2 protocol includes a media access controlprotocol. The media access control protocol used by a network clientadapter is Ethernet or Fibre Channel. Each of the network clientadapters is operable to convert a received optical signal to anelectrical signal. Each network client adapter is operable to select aframe within the electrical signal associated with the network clientadapter. The optical local area network further includes a client thatincludes a network interface card, the network interface card includingone of the network client adapters. The client is selected from thegroup consisting of a workstation, a personal computer, a disk storagearray, a server, a switch, and a router.

In general, in another aspect, the invention includes an optical localarea network including a hub; a plurality of external nodesinterconnected by a passive optical distribution fabric, wherein theexternal nodes are located external to the hub, and the hub is operableto control traffic across all nodes; adaptors at each external noderesponsive to hub instruction; and an interface coupled to the hubcoupling signals received from any individual external node fordistribution to all external nodes.

Aspects of the invention may include one or more of the followingfeatures. The hub includes an internal node coupled to the passiveoptical distribution fabric. The hub is operable to measure responsedelay between the hub and external nodes. The hub is operable toallocate slots for external nodes dynamically. Slot allocations are madeto guarantee external nodes have a minimum bandwidth. The optical localarea network further includes splitters coupled between the hub andexternal nodes. Traffic arriving at one or more external nodes includesEthernet traffic. Traffic arriving at one or more external nodesincludes Fibre channel traffic. The hub includes an optical module. Atleast one of the external nodes is located within an optical moduleexternal to the hub.

Implementations of the invention may include one or more of thefollowing advantages. A network manager in an optical local area networkcan provide switching functions of a hub, a switch or a router. A switchconfiguration in which network managers are aggregated enables a highperformance network in a compact apparatus. Connectivity of networkmanagers and network client adapters to existing conventional routersand switches using industry standard form factor optical modules enablesa high performance network upgrade with minimal new equipment. A networkclient switch can support multiple physical layer ports withoutnecessarily requiring a Layer-2 MAC or switching elements and theassociated routing tables and packet memory. The number of opticaltransceivers and switching elements used to sustain the same number ofcomputing nodes in a LAN via a point-to-multipoint optically couplednetwork configuration is reduced, thus saving the majority of expensedescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an optical local area network.

FIG. 2 is schematic diagram showing frame structures.

FIGS. 3A and 3B are schematic diagrams showing frame structures.

FIG. 4 is a flowchart for a network operating process.

FIG. 5 is a flowchart for a response delay process.

FIGS. 6A-6C are diagrams of optical local area networks utilizing a hubconfiguration

FIGS. 7A-7D are diagrams of optical local area networks utilizing aswitch configuration.

FIG. 8 is a diagram of an optical local area network.

FIGS. 9A and 9B are block diagrams of switches.

DETAILED DESCRIPTION

Referring to FIG. 1, a high-level schematic of an optical local areanetwork 50 includes a network manager (NM) 100 at the head end of apassive optical distribution fabric (ODF) 102. The NM 100 acts as acentral transmission point and an overall controlling device for theoptical local area network 50. On another end, the ODF 102 is terminatedby a plurality of (in one implementation, generally similar) networkclient adapters (NCAs) 104A, 104B, 104C. Herein the NCA 104A, NCA 104B,NCA 104C, are also referred to collectively as NCAs 104. Though threeNCAs 104 are shown more or fewer NCAs may be included in the opticallocal area network 50.

The NM 100 transmits/receives data to/from the NCAs 104 in the form ofmodulated optical light signals of known wavelength through the ODF 102.The transmission mode of the data sent over the ODF 102 may becontinuous, burst or both burst and continuous modes. Both NM 100 andNCAs 104 may transmit light signals having a same wavelength. In oneimplementation, the light signals are polarized and the polarization oflight transmitted by the NM 100 is perpendicular to the polarization ofthe light transmitted by the NCAs 104. Alternatively, the transmissionscan be-made in accordance with a time-division multiplexing scheme orsimilar protocol.

In another implementation, bi-directional wavelength-divisionmultiplexing (WDM) may be used. Bi-directional WDM is herein defined asany technique by which two optical signals having different wavelengthsmay be simultaneously transmitted bi-directionally with one wavelengthused in each direction over a single fiber. In yet anotherimplementation, bi-directional dense wavelength-division multiplexing(DWDM) may be used. Bi-directional DWDM is herein defined as anytechnique by which more than two optical signals having differentwavelengths may be simultaneously transmitted bi-directionally with morethan one wavelength used in each direction over a single fiber with eachwavelength unique to a direction. For example, if bi-directional WDM isused, the NM 100 may transmit data to an NCA 104A, 104B, 104C utilizinga first wavelength of modulated light conveyed via a fiber 105A, 105B,105C, respectively, in the ODF 102 and, similarly, the NCAs 104A, 104B,104C may transmit data via the same fiber 105A, 105B, 105C,respectively, in the ODF 102 to the NM 100 utilizing a second wavelengthof modulated light. Because only a single fiber is used (e.g., betweenthe NM 100 and each respective NCA 104), this type of transmissionsystem is commonly referred to as a bi-directional transmission system.Although the optical local area network 50 illustrated in FIG. 1includes an NM 100 in communication with a plurality of NCAs 104 using aplurality of fibers, other implementations of optical local areanetworks 50 may be used. In some implementations, the NCAs 104 aregenerally similar. In other implementations, the NCAs 104 may differ inone or more aspects.

The NM 100 includes network management communication logic and memory(NM-CLM) 106 block, a network management optical interface (NM OpticalInterface) 108 block and an optical distribution fabric interface (ODFInterface) 110 block. The NM-CLM 106 includes a network manager engine(NM Engine) 112 block, a transmit framer (Tx Framer) 114 block and areceive framer (Rx Framer) 115 block.

The NM Engine 112 is a control module that performs various processingand scheduling functions of an NM 100. The Tx Framer 114 frames outgoingdata from the NM Engine 112 in accordance with a framing protocol thatis in-use. The Rx Framer 115 receives incoming frames and recoversappropriate data and messages to pass on to the NM Engine 112. The NMOptical Interface 108 is controlled by the NM-CLM 106 using, forexample, bus 109. The NM Optical Interface 108 converts electricalsignals carrying data from the Tx Framer 114 to optical signals, forexample, by modulating a laser (not shown) included in the NM OpticalInterface 108 and transmitting the laser output to the ODF interface110. The NM Optical Interface 108 also receives optical signals from theODF interface 110 and converts the optical signals to electrical signalscarrying data that is then transferred to the Rx Framer 115. Thus, theNM Optical Interface 108 functions as an “optical-electrical converter”that can convert a signal from an optical signal to electrical signal orfrom an electrical signal to an optical signal.

The ODF Interface 110 includes an optical splitter 116 and a pluralityof ODF Ports 117A, 117B, 117C, etc. For example, the optical splitter116 can be a 1:n splitter (where n is at least 2) that splits lightcoming from the NM Optical Interface 108 into n portions of lightcoupled into n optical ports, respectively. The optical ports (e.g., ODFPorts 117) can be coupled to one or more optical waveguides. In oneimplementation, each ODF Port 117 is coupled to an optical waveguide.The optical waveguides can be, for example, single mode or multimodefibers that guide received/transmitted light to/from respective ODFPorts 117A, 117B, 117C, etc. The 1:n splitter (or equivalently, n:1combiner) also directs light from any of the ODF Ports 117A, 117B, 117C,etc. received over one of the optical waveguides to the NM OpticalInterface 108. ODF Ports 117A, 117B, 117C, etc. include optical fiberconnector sockets (e.g., SC, LC, FC, ST, or MU connector sockets) forcoupling to the optical waveguides.

The ODF 102 can include any of a variety of passive optical componentsincluding optical fibers (e.g., single mode fibers, multimode fibers),optical connectors, fiber splices, passive branching components (e.g.,passive splitters) and passive optical attenuators.

In this implementation, the NCAs 104 each include a network clientcommunication logic and memory (NC-CLM) 120 block, a network clientoptical interface (NC Optical Interface) 122 block and an ODF port 124.The NC-CLM 120 block includes an Adaptation Unit 126 block, a networkclient engine (NC Engine) 128 block, a transmit framer (Framer) 130block and a receiver framer (Deframer) 131 block. The NC Engine 128 is acontrol module that performs various functions associated with an NCA104, such as responding to messages from the NM 100. The Framer 130frames outgoing data from the NC Engine 128 in accordance with a framingprotocol that is in-use. The Deframer 131 receives incoming frames andrecovers appropriate data and messages to pass on to the NC Engine 128.The adaptation unit 126 receives and transmits data and messages in theform of frames, packets or cells according to one or more externalprotocol(s). External controls, data and messages can be received usingthe network interface 136. The responsibilities of the adaptation unit126 may include providing buffering, data and/or message filtering andtranslation between the external protocol(s) and the protocol of theoptical local area network 50. The adaptation Unit 126 includes egressqueue 132 block and ingress queue 133 block. Egress and ingress queues132, 133 can be of the form of memory and are used for buffering receiveand transmit data and messages, respectively. The adaptation unit 126can filter out or drop data and/or messages that are not intended toegress through its network interface 136. Filtering can be based on thedestination address of the data and/or messages according to theexternal protocol in-use. Additionally, the adaptation unit 126 canfilter out or drop data and/or messages that are not intended to ingressthrough its network interface 136. Filtering can be based on equalvalues for the source and destination addresses of the data and/ormessages according to the external protocol in-use. The NC OpticalInterface 122 is controlled by the NC-CLM 128 using bus 134. The NCOptical Interface 122 converts electrical signals carrying data from theFramer 130 block to optical signals, for example, by modulating a laser(not shown) included in the NC Optical Interface 122 and transmittingthe laser output to the ODF port 124. The NC Optical Interface 122 alsoreceives optical signals from the ODF port 124 and converts the opticalsignals to electrical signals carrying data that is then transferred tothe Deframer 131 block. The ODF port 124 includes an optical fiberconnector socket (e.g., an SC, LC, FC ST, or MU connector socket).

The. NCAs 104 can be coupled to data link layer devices (not shown) orphysical layer devices (not shown) using network interface 136. The datalink layer devices and physical layer devices are network devices thatoperate at a Layer-2 or Layer-I respectively, according to the OpenSystems Interconnect (OSI) 7-layer reference model. Furthermore, thesenetwork devices may comply with industry standard specifications such asIEEE 802.3 and Fibre Channel (incorporated herein by reference).Consequently, the network interface 136 may be an MII, GMII, XGMII, XAUIor SPI type interface. Other Layer-2 and Layer-I type interfacespecifications may also be used.

The optical local area network 50 transfers data between an NM 100 andthe NCAs 104 in the form of downstream frames (NM 100 to NCAs 104) andupstream “virtual frames” (NCAs 100 to NM 104). Downstream frames fromthe NM 100 are transmitted into the ODF 102 in an essentially continuoussequence of constant period frames. In one implementation, downstreamframes have a period of 125 μs, and transfer data downstream at a rateof approximately 10 Gb/s, although other periods and rates may be used.The ODF Interface 110 and potentially the ODF 102 split the downstreamtransmissions passively so that all NCAs 104 receive the frames in agenerally broadcast manner. In the upstream direction, separatetransmissions from the plurality of NCAs 104 are transmitted as bursttransmissions or in slots which are combined in a virtual frame so thatthe separate burst transmissions do not collide when they arrive at theNM 100. In one implementation, the virtual upstream frames haveessentially the same period as the downstream frames, and upstream datatransmissions are transmitted at a rate approximately equal to thedownstream rate. Alternatively, different upstream and downstream ratesmay be used.

FIG. 2 is a schematic timing and framing diagram, showing overallstructure of a downstream frame 200, and a virtual upstream frame 202 inan implementation of a framing protocol. Referring now to FIGS. 1 and 2,each downstream frame 200 includes a header 204 and a payload section206. The downstream header 204 includes a downstream synchronization (DSSync) 208 section, a station management 210 section, two sectionscontaining the number of NCAs 104 in communication with the NM 100 (# ofNCAs) 212, 214 and an upstream slot allocation (US slot allocation) 216section. The DS Sync 208 section includes a consecutive sequence of bitsthat enables receiving NCAs 104 to identify a beginning of thedownstream frame 200 and thus acts as starting marker for frame timingthroughout the optical local area network 50. The number of NCAs 104 incommunication with the NM is sent twice 212,214 to ensure correctinterpretation of the US slot allocation section 216. The order ofdownstream header sections 210,212,214,216 after a DS Sync 208 maydiffer in other implementations.

During each network period 218 defined by respective adjacent downstreamheaders, each NCA 104 is able to send upstream data. The virtualupstream frame 202 is partitioned into slots, where a “slot” correspondsto a fixed number of bits or a fixed length of time within a virtualframe. For each network period 218, the NM 100 allocates each NCA 104respective slots within which an NCA is able to transmit data upstream.Each slot allocation includes a start slot number and end slot number(also referred to as start time and end time), relative to the startingmarker defined by a DS Sync 208 from the next network period after anNCA 104 receives a slot allocation. In alternative implementations, astart slot number and a length of time during which a specific NCA 104is permitted to transmit may be sent instead of a start slot number andan end slot number. Slot allocation start and end numbers are allocatedwithin the virtual upstream frame so that slot allocations do notoverlap, ensuring that there are no collisions of data from differentNCAs 104 at the NM 100. The allocations can be determined by the NMEngine 112 based on total upstream bandwidth requests and can becommunicated to NCAs 104 in the downstream frame US slot allocation 216section. The US slot allocation 216 section includes start and end slotnumbers pertaining to and identified to specific NCAs 104 (as shown in220 and 222). Slot allocations assigned to NCAs 104 can be dynamic andmay be changed from network period to network period.

The upstream frame 224 includes header 226 and payload 228 sections. Theheader 226 includes a preamble 230 section, a frame delimiter(Delimiter) 232 section and a station management 234 section. Thepreamble 230 section includes a consecutive sequence of bits designed toaid an NM 100 in synchronizing to the bit clock of a respectivetransmitting NCA 104. The Delimiter 232 includes a consecutive sequenceof bits designed to aid an NM 100 in synchronizing to and recognizingthe beginning of an upstream frame 224.

Each downstream frame 200 and upstream frame 224 includes a payloadsection 206, 228 respectively, in which data to and from NCAs 104 (fromthe network interface 136) are transferred. FIG. 3A is a schematicshowing the payload in downstream and upstream framing, showing that thepayload of both upstream and downstream may contain a single adaptationdata unit (ADU) 300. ADUs 300 are output units of data from anadaptation unit 126, where the adaptation unit 126 has processed datareceived from the network interface 136 for transfer across the opticallocal network 50. For example, in one implementation the adaptation unit126 receives Ethernet media access control frames (MAC frames) via aGMII interface (as an implementation for the network interface 136) andremoves the MAC frame's preamble and start of frame delimiter (SFD)fields with the remaining fields of the MAC frame encapsulated in an ADU300. Additionally, in one implementation the adaptation unit 126receives Fibre Channel (FC) FC-2 frames through a serial interface (asan implementation of the network interface 136) and removes the FC-2frame's start of frame and end of frame fields with the remaining fieldsof the FC-2 frame encapsulated in an ADU 300.

In another example, the adaptation unit 126 can receive IEEE 802.3 MACframes via a GMII interface and form an ADU 300 with the entire MACframe included (i.e., encapsulate the entire MAC frame). In yet anotherexample, the adaptation unit 126 can receive FC-2 frames through aserial interface (as an implementation for the network interface 136)and form an ADU 300 with the entire FC-2 frame included (i.e.,encapsulate the entire FC-2 frame).

In one implementation, the payload 204, 232 of downstream frames 200 andupstream frames 224 may include multiple consecutive sub-frames.Referring to FIGS. 1 and 3B, a sub-frame includes a sub-frame header 302section and a sub-frame payload 304 section. A sub-frame header 302section includes a payload length indicator (PLI) 308 and cyclicredundancy check (CRC) 310 section that covers the PLI 308. CRCsections, although not shown, may be used in the downstream 200 andupstream 224 frames as well. The sub-frame payload 304 section includesa type 312 section, a CRC 314 that relates to the type 312 section, apayload data unit (PDU) 316 and optionally a CRC 318 that relates to thePDU 316. The PLI 308 gives an indication of the length, e.g., in bits,of the sub-frame payload 304 section immediately following the sub-frameheader 302. The type 312 section gives an indication of the type of datain the PDU 316. An adaptation unit 126 may receive data from a mixtureof protocols essentially simultaneously (as described below) and the useof sub-frames allows the data to be transferred across the networkensuring quality of service or class of service. An adaptation unit 126uses sub-frames by placing received data in the PDU 316, indicating thetype of data received in the type 312 section and entering the length ofthe sub-frame payload 304 in the PLI 308 section.

The optical local area network 50 operates according to an exemplaryprocess illustrated in FIG. 4. Referring now to FIGS. 1 and 4, after anNM 100 is powered on 400, the NM 100 sends out 402 one or moremessage(s) requesting new NCAs 104 (NCAs 104 that the NM 100 is unawareof) to identity themselves by reporting to the NM 100 with theirrespective serial number. The NM 100 also sends out 402 networkparameters including initial NCA transmit power levels using, forexample, a station management message(s). The NCAs 104 respond usingslot allocation(s) given by the NM 100 for new NCAs 104 to respond.After successfully receiving new NCA serial numbers, the NM 100 assignseach new NCA 104 a network identification number (NC-ID) and requests404 the new NCA 104 to adjust its transmitting power level. In oneimplementation, the NM 100 sends these requests in a station managementmessage. The respective new NCAs 104 use the assigned NC-ID to interpretspecific messages of concern (i.e., addressed) to a given NCA 104. TheNM 100 initiates 406 a response delay process to determine the delay inresponses between the new NCA and the NM 100. After performing 419 theresponse delay process, the NM 100 enters normal operation in whichnetwork data is transmitted and received 408 across the optical localarea network 50.

When an NCA 104 is powered on 410, the NCA 104 attempts to synchronize412 to downstream frames by searching for the DS Sync 208. Aftersuccessful downstream synchronization, the NCA 104 interprets 414network parameters received via downstream station management messages404, adjusts its initial transmit power level and awaits instructions(e.g., a message) for new NCAs 104. The instructions include a slotallocation for new NCAs 104 to respond 416 to the NM 100 with the NCA's104 serial number. Once the NCA 104 has sent its serial number the NCA104 is then assigned an NC-ID by the NM 100. The NCA 104 then enters awaiting loop (e.g., for a station management message from the NM 100 toadjust its transmit power level). In response to a request to settransmit power level, the NCA 104 adjusts the transmit power level 418.The NCA 104 then enters a waiting loop again (e.g., until receipt of amessage from the NM 100 to initiate a response delay process). Uponreceipt of an instruction to begin a response delay process, the NCA 104can, in cooperation with the NM 100, determine the delay between therespective network elements (not shown as part of the process flow). Thedetails of the response delay process are described in greater detailbelow. After the NCA 104 and NM 100 complete the response delay process,the NCA 104 may adjust 420 its alignment with the network period toaccount for downstream and upstream transmission delay. The NCA 104 thenenters its normal operation state in which network data is received andtransmitted 422.

FIG. 5 shows one implementation for executing a response delay process500. The response delay process 500, is a process to determine the delayin NM downstream transmission to NM upstream reception of a message ornetwork data transmission. Referring now to FIGS. 1, 2 and 5, the NM 100starts 501 the delay process with a new NCA 104 or with an NCA 104 thatmay cause upstream transmission collisions. The NM 100 assigns one ormore slot(s) to the target NCA 104 (i.e., the new NCA or one NCA thatmay cause a collision in upstream communication) to respond with aresponse delay message. The NM 100 generates 502 a silence period in theupstream virtual frame 202 (e.g., by not assigning or granting any slotsfor that period) around the slot(s) assigned to the target NCA 104. Thesilence period ensures no upstream collisions will occur. The NM 100sends 504 a message to the NCA 104 to respond with a response delaymessage and informs the NCA 104 of its slot(s) assignment to respond.Thereafter, the NCA 104 responds 506 to the NM 100 at the appropriateslot time. The NM 100 receives the NCA 104 response delay message andcalculates 508 the transmission delay. In one implementation, the NM 100transmits 510 the result of the response delay calculation to the NCA104 and the NCA 104 aligns 512 itself to the proper network period.

The NM 100 may assign, schedule or grant slot allocations in a number ofways (e.g. according to fixed time-division multiplex or statisticaltime-division multiplex schemes). In one implementation the slotallocations are scheduled to give the NCs 104 a guaranteed minimumupstream transfer rate. The rate may be determined by dividing themaximum upstream data rate by the number of NCAs 104. In anotherimplementation, the NM 100 receives status information about the NCAs104 egress 132 and ingress 133 queue status. The NM 100 can scheduleslot allocations that best minimize the depth of the egress 132 andingress 133 queues to minimize transmission delays ensuring quality ofservice (QOS) or class of service (COS).

FIGS. 6A-6C, 7A-7C and 8 are illustrations of implementations of theoptical local area network 50. In one implementation shown in FIG. 6A,an NM 100 may function in a hub configuration 600 networking clientsincluding workstations 602, personal computers (PC) 604 and Ethernetswitches 618 together using the Ethernet protocol. The workstations 602and PCs 604 are connected to the hub configuration 600 with a networkinterface card (NIC) 606 containing an NCA 104 and a NIC controller 608.In one implementation of the NIC 606, the NIC controller 608 includes aGMII interface, an Ethernet MAC and a peripheral component interconnect(PCI) bus interface. The NCA 104 communicates to the NIC controller 608through the GMII interface. Ethernet switches 618 are connected to thehub configuration 600 with a network adaptor 621A containing an NCA 104.Ethernet switches 618 can be conventional Ethernet switches. In oneimplementation of the network adaptor 621A, the network interface 136 isa GMII interface.

In another implementation shown in FIG. 6B, the hub configuration 600can network disk storage array devices 612, servers 614 and FC switches619 together using the Fibre Channel (FC) protocol. This implementationmay be described as a Storage Area Network (SAN). The disk. storagearray devices 612 and servers 614 are connected to the hub configuration600 with a host bust adaptor (HBA) 607. In one implementation of HBA607, the HBA controller 609 includes a serial interface, FC controllerand a PCI bus interface. FC switches 619 are connected to the hubconfiguration 600 with a network adaptor 621B containing an NCA 104. FCswitches 619 can be conventional FC switches. In one implementation ofthe network adaptor 621B, the network interface 136 is a serialinterface.

In yet another implementation of the optical local area network 50 shownin FIG. 6C, the hub configuration 600 may network clients such asworkstations 602, PCs 604, disk storage array devices 612, servers 614and switches 618,619 (FIG. 6B) using both Ethernet and FC protocolsconcurrently. NICs 606 can connect a particular client to the hubconfiguration 600 using the Ethernet protocol. HBAs 607 can connect aparticular client to the hub configuration 600 using the FC protocol.For example, workstations 602, PCs 604 and switches 618 can communicatewith the hub configuration 600 using Ethernet protocol while diskstorage array devices 612 and servers 614 can communicate with the hubconfiguration 600 using FC protocol. The ODF 102 (not shown) of theoptical local area network 50 can include splitters 620. Hubconfiguration 600 can also connect to a switch 618 using an adaptor card621A. Adaptor card 621A includes an NCA 104 with a respective networkinterface 136 (e.g., GMII, XAUI, Serial). Switch 618 may be, forexample, a switch in a conventional Ethernet LAN 622.

One or more NMs 100 can interface to a switching device (e.g., a Layer-2switch or a Layer-3 switch) to process frames from the various NCAs 104according to a communication protocol of the switching device. Referringto FIG. 7A, a switch configuration 704 includes multiple NMs 100A, 100B,100C in communication with a Layer-2 switch device 700 which is infurther communication with an uplink port 702. In alternativeimplementations, the Layer-2 switch device 700 may be in communicationwith a plurality of uplink ports (not shown). Though three NMs 100A,100B, 100C are shown more or fewer NMs 100 may be in communication witha Layer-2 switch device 700 included in the switch configuration 704.Each NM 100A, 100B, 100C includes an adaptation unit 706 incommunication with a NM Engine (not shown). The adaptation unit 706receives and transmits data and messages in the form of frames, packetsor cells according to the Layer-2 switch device 700 via a switchinterface 708. Adaptation unit 706 can provide buffering, data and/ormessage filtering and translation between the protocol of the Layer-2switch device 700 and the protocol of the optical local area network 50.The adaptation unit 706 includes an egress queue block (not shown) andan ingress queue block (not shown). Egress and ingress queues can be ofthe form of memory and are used for buffering receive and transmit dataand messages, respectively. In one implementation of the NMs 100A, 100B,100C, all upstream traffic received by an NM 100 is passed through theswitch interface 708 to the Layer-2 switch device 700. All downstreamtraffic transmitted by an NM 100 is received by the NM 100 through theswitch interface 708. In another implementation upstream trafficreceived by an NM 100 can be filtered based on destination address toeither pass data and/or messages back to one or more NCAs 104multiplexed in downstream traffic (e.g. hairpinning) or to the Layer-2switch device 700 through the switch interface 708. The fiberconnections 105 form a first ODF for connecting NM 100A with one or moreNCAs. The fiber connections 710 form a second ODF for connecting NM 100Bwith one or more NCAs. The fiber connections 712 form a third ODF forconnecting NM 100C with one or more NCAs.

In one implementation of an optical local area network 50 shown in FIG.7A, the switch configuration 704 is used to network workstations 602,PCs 604 and a Ethernet switch 618 together using the Ethernet protocolwith appropriate NICs 606 as described above. The switch configuration704 includes a Layer-2 switch (e.g., Layer-2 switch device 700) thatimplements an Ethernet MAC and switching functions. The optical fibers105, 710, 712 connecting the workstations 602, PCs 604 and Ethernetswitches 618 to the switch configuration 704 can be associated withdifferent NMs 100A, 100B, 100C depending on which fiber connections areused. The uplink port 702 of switch configuration 704 can connect to anEthernet switch and/or router (not shown).

In another implementation of an optical local area network 50 shown inFIG. 7B, the switch configuration 704 is used to network one or moredisk storage array devices 612, servers 614 and FC-2 switches 619 using,for example, the FC protocol with appropriate HBAs 607 as describedabove. This implementation may also be described as a Storage AreaNetwork (SAN). The switch configuration 704 includes a Layer-2 switch(e.g., Layer-2 switch device 700) that implements an FC-2 controller andswitching functions. The optical fibers 105, 710, 712 connecting thedisk storage array devices 612, servers 614 and FC-2 switch 619 to theswitch configuration 704 can be associated with different NMs 100A,100B, 100C depending on which fiber connections are used. The uplinkport 702 of switch configuration 704 may connect to an FC-2 switchand/or router (not shown). FC-2 switches 619 can be a conventional FC-2switch.

In yet another implementation of an optical local area network 50 shownin FIG. 7C, a switch configuration 704 is used to network workstations602, PCs 604, ‘disk storage array devices 612, servers 614 and otherswitches (e.g. an Ethernet switch 618) together using, for example, bothEthernet and FC protocols concurrently in a manner described previously.The switch configuration 704 includes a Layer-2 switch (e.g. Layer-2switch device 700) that implements both an Ethernet MAC and FC-2controller with switching functions. Layer-2 switch device 700 can beimplemented by a packet processor or network processor. The opticalfibers 105, 710, 712 connecting the workstations 602, PCs 604, diskstorage array devices 612, servers 614 and t switches to the switchconfiguration 704 can be associated with different NMs 100A, 100B, 100Cdepending on which fiber connections are used. The uplink port 702 ofswitch configuration 704 may connect to an Ethernet or FC-2 switchand/or router (not shown).

In yet another implementation of an optical local area network 50, animplementation of switch configuration 705 containing an NM 100, anadaptation unit 706 and an uplink port 702 is shown in FIG. 7D. Switchconfiguration 705 can be used to network workstations 602, PCs 604 andother switches 618 in a manner described previously. The NM 100 is incommunication with a Layer-2 switch device (not shown) through theuplink port 702 that is connected to a switch. The connection betweenuplink port 702 and switch 618 can be a physical layer connection 714(e.g., 1000 BASE-SX,1000 BASE-LX). Ethernet switch 618 can be aconventional Ethernet switch.

In some implementations of switch configurations 704, 705 the uplinkport 702 can be an NCA adaptor (not shown) similar to 621A, 621B whereinthe network interface 136 and switch interface 708 are coupled using thesame interface standard (e.g., XAUI, Serial, Parallel), thus enablingthe uplink port 702 to connect to other hub configurations 600 andswitch configurations 704 (FIGS. 7A-7C), 705 (FIG. 7D).

In another implementation of an optical local area network 50 shown inFIG. 8, NM 100 and NCA 104 may be implemented in optical modules. Anetwork manager in an optical module (NM-OM) 800 is provided that, inone implementation, conforms to an industry standard form factor andincludes an NM-CLM 803 that includes an adaptation unit 706 to transferdata into and out of a network interface (e.g., switch interface 708).The NM-OM 800 also includes a NM Optical interface 108 and an ODF port117A. In one implementation, the optical module NM-OM 800 conforms to anindustry standard Multi-source agreement (MSA) form factor (e.g., 300pin, XENPAK, X2, XPAK, XFP or SFP). A network client adaptor in anoptical module (NC-OM) 802 can be provided that, in one implementation,also conforms to an industry standard form factor and includes an NCA104. For example, the optical module NC-OM may conform to an MSA formfactor (e.g., 300 pin, XENPAK, X2, XPAK, XFP or SFP).

The NM-OM 800 can connect to a conventional router 804 that has opticalmodule ports 806 using the router's switch interface (e.g., XAUI orSerial). The NM-OM 800 is in optical communication with an opticalsplitter 810 that splits light among and collects light fromworkstations 602, PCs 604, disk storage array devices 612, servers 614and switches using appropriate NICs 606 and/or NC-OM 802 as previouslydescribed. The Ethernet Layer-2/3 switch 808 may be of conventionaldesign and include an uplink port, that in one implementation, conformsto an industry standard optical module form factor. The EthernetLayer-2/3 switch 808 can communicate with the NM-OM 800 in router 804 byusing an NC-OM 802 via network interface 136 (e.g., XAUI or Serial).

The Ethernet Layer-2/3 switch 808 is further detailed in FIG. 9A. In theEthernet Layer-2/3 switch 808, an NC-OM 802 is in communication with aLayer-2 switch 900 by means of a MAC (not shown) using a networkinterface 136 (e.g., XAUI or Serial). Ethernet Layer-2/3 switch 808 alsoincludes physical layer ports (PHY ports) 902 that, in oneimplementation, form a conventional Ethernet LAN (e.g., Ethernet LAN 622of FIG. 8) connecting network clients such as workstations 602 and PCs604.

An implementation of an alternative configuration for a switch is shownin FIG. 9B. FIG. 9B is an illustration of an NC-Switch 910, in which noconventional Layer-2 switch and MAC is used. NC-Switch 910 includes anNCA 912 and multiple PHY ports 902. Each PHY port may perform wireline(e.g., 10/100/1000 BASE-T, DSL) or wireless (e.g., IEEE 802.11, IEEE802.16) physical layer communications with conventional LAN clients. Inthis implementation, the adaptation unit 126 supports multiple networkinterfaces 136. The switching function previously performed by theLayer-2 switch (e.g., Layer-2 switch 900 of FIG. 9A) is consolidated tothe switch or router in communication with an NM 100 in a switchconfiguration 704 (as described above) or an NM-OM 800 (e.g. asillustrated in FIG. 8 an NC-Switch 910 in communication with an NM-OM800). Alternatively, the switching function previously performed by theLayer-2 switch is consolidated to Layer-2 switches (not shown) incommunication with other NCAs 104 networked in a hub configuration 600.

In hub configuration 600 (e.g. FIGS. 6A-6C) of the optical local areanetwork 50, flow control, denial of service and other networkadministration functions are dependent on external Layer-2 devices incommunication with NCAs 104 (for example, the Ethernet MAC or FC-2controller in the NIC controller 608 dependent on the implementation aspreviously discussed). In switch configurations 704 (e.g. FIGS. 7A-7C)of the optical local area network 50, flow control, denial of serviceand other network administration functions are further dependent on theexternal Layer-2 device 700 in communication with NMs 100, in additionto the Layer-2 devices external and in communication with NCAs 104 aspreviously mentioned.

Although the invention has been described in terms of particularimplementations, one of ordinary skill in the art, in light of thisteaching, can generate additional implementations and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof

What is claimed is:
 1. A method for operating a local area network (LAN)client for a passive optical local area network (LAN), the passiveoptical LAN disposed to having one or more passive optical splitters forcoupling the LAN client over one or more optical fibers to the head endof the passive optical LAN, the method for operating the LAN client forthe passive optical local area network comprising: receiving from anoptical port of the LAN client a downstream optical signal on adownstream wavelength wherein the downstream optical signal includesdownstream control and downstream data information and wherein thedownstream control information includes at least one upstream bandwidthallocation for the LAN client; receiving user data from an electricalinterface of the LAN client; and transmitting an upstream optical signalthrough the optical port of the LAN client on an upstream wavelengthresponsive to the at least one upstream bandwidth allocation for the LANclient and wherein the upstream optical signal includes upstream controland upstream data information and, wherein the upstream data informationincludes at least a portion of the user data.
 2. The method foroperating the LAN client for the passive optical local area network ofclaim 1, wherein the LAN client includes a passive optical LAN protocolprocessor.
 3. The method for operating the LAN client for the passiveoptical local area network of claim 2, wherein the LAN client includesan Ethernet MAC that communicates to the passive optical LAN protocolprocessor.
 4. The method for operating the LAN client for the passiveoptical local area network of claim 2, wherein the LAN client includes adevice for processing OSI Layer 3 communications that communicates tothe passive optical LAN protocol processor.
 5. The method for operatingthe LAN client for the passive optical local area network of claim 2,wherein the passive optical LAN protocol processor is assigned a networkidentification address included in a message in a downstream opticalsignal processed by the passive optical LAN protocol processor andwherein the passive optical LAN protocol processor uses the networkidentification address for processing downstream data informationaddressed to the LAN client for the passive optical LAN.
 6. The methodfor operating the LAN client for the passive optical local area networkof claim 2, wherein the passive optical LAN protocol processor performsoperation administration and maintenance (OAM) message processing. 7.The method for operating the LAN client for the passive optical localarea network of claim 1, wherein a downstream optical signal includes aresponse delay information message and wherein the LAN client adjuststhe timing of transmitting upstream optical signals responsive to theresponse delay information message.
 8. The method for operating the LANclient for the passive optical local area network of claim 1, wherein adownstream optical signal includes a message regarding an optical powerlevel of the LAN client's upstream optical signals and the responsive toreceiving the message the LAN client adjusts its transmit optical powerlevel.
 9. The method for operating the LAN client for the passiveoptical local area network of claim 1, wherein a downstream opticalsignal includes a message requesting new LAN clients to respond byidentifying themselves and responsive to receiving the message the LANclient sends an upstream optical signal that includes the serial numberof the LAN client.
 10. The method for operating the LAN client for thepassive optical local area network of claim 1, wherein the at least oneupstream bandwidth allocation for the LAN client includes start and endtime slot numbers.
 11. The method for operating the LAN client for thepassive optical local area network of claim 1, wherein the at least oneupstream bandwidth allocation for the LAN client includes start time andlength of time.
 12. The method for operating the LAN client for thepassive optical local area network of claim 1, wherein the downstreamcontrol information includes a consecutive sequence of bits for the LANclient to identify the beginning of a downstream frame, and wherein thedownstream frame includes the downstream control and data information.13. The method for operating the LAN client for the passive opticallocal area network of claim 1, wherein the upstream control informationincludes LAN client queue status information.
 14. The method foroperating the LAN client for the passive optical local area network ofclaim 1, wherein in the upstream optical signal is emitted in one ormore upstream slots of time forming one or more upstream frames asgoverned by the at least one upstream bandwidth allocation.
 15. Themethod for operating the LAN client for the passive optical local areanetwork of claim 1, wherein the optical port of the LAN client isdisposed to couple to at least one optical fiber.
 16. The method foroperating the LAN client for the passive optical local area network ofclaim 1, further comprising processing the downstream data informationaccording to an Open Systems Interconnect (OSI) Layer 3 protocol by theLAN client for a passive optical local area network.
 17. A method foroperating a local area network (LAN) client for a passive optical localarea network (LAN), the passive optical LAN disposed to having one ormore passive optical splitters for coupling the LAN client over one ormore optical fibers to the head end of the passive optical LAN, themethod for operating the LAN client for the passive optical local areanetwork comprising: processing a received optical signal on a firstwavelength received through an optical port of the LAN client whereinthe received optical signal includes control and downstream datainformation and wherein the control information includes at least onetransmit bandwidth allocation for the LAN client; receiving Ethernetdata from an electrical interface of the LAN client; and emitting atransmit optical signal on a second wavelength through the optical portof the LAN client responsive to the at least one transmit bandwidthallocation for the LAN client, and wherein the transmit optical signalincludes control and data information, and wherein the data informationincludes at least a portion of the Ethernet data.
 18. A method foroperating a local area network (LAN) client for a passive optical localarea network (LAN), the passive optical LAN disposed to having one ormore passive optical splitters for coupling the LAN client over one ormore optical fibers to the head end of the passive optical LAN, themethod for operating the LAN client for the passive optical local areanetwork comprising: processing a received optical signal on a firstwavelength received through an optical port of the LAN client whereinthe received optical signal includes control and downstream datainformation and wherein the control information includes at least onetransmit bandwidth allocation for the LAN client; processing thedownstream data information according to an Open Systems Interconnect(OSI) Layer 3 protocol; receiving Ethernet data from an electricalinterface of the LAN client; and emitting a transmit optical signal on asecond wavelength through the optical port of the LAN client responsiveto the at least one transmit bandwidth allocation for the LAN client,and wherein the transmit optical signal includes control and datainformation, and wherein the data information includes at least aportion of the Ethernet data.
 19. The method for operating the LANclient for the passive optical local area network of claim 18, whereinthe LAN client includes a passive optical LAN protocol processor. 20.The method for operating the LAN client for the passive optical localarea network of claim 19, wherein the LAN client includes an EthernetMAC that is communicates with the passive optical LAN protocolprocessor.
 21. The method for operating the LAN client for the passiveoptical local area network of claim 18, wherein the LAN client includesa device for processing the OSI Layer 3 protocol that is communicateswith the passive optical LAN protocol processor.